1. Field of the Invention
The present invention relates to a droplet ejecting apparatus and in particular to such a droplet ejecting apparatus which includes a piezoelectric body that can be produced at low cost, be easily polarized, and enjoy improved deformation efficiency at a given drive voltage.
2. Discussion of Related Art
There have conventionally been known various sorts of ink jet recording heads each for use in an ink jet recording apparatus. For example, Japanese Patent No. 2913806 or its corresponding U.S. Pat. No. 5,266,964 discloses an ink jet recording head including a cavity plate having a pressure chamber in which ink is accommodated, and a sheet-stacked-type piezoelectric element fixed to the cavity plate to close the opening of the pressure chamber. In this ink jet recording head, when a drive voltage is applied to first and second internal electrodes provided in the sheet-stacked piezoelectric element that is polarized, in advance, in the direction of stacking of piezoelectric sheets thereof, an electric field is produced in the stacked piezoelectric element, in a direction perpendicular to the direction of polarization thereof, so that the piezoelectric element is deformed in a so-called shear mode. This deformation of the piezoelectric element results in changing the volume of the pressure chamber, so that a droplet of ink is ejected from a nozzle communicating with the pressure chamber.
The above-indicated document additionally discloses a method of manufacturing the stacked piezoelectric element. The disclosed method includes a polarizing step in which, first, one or more internal electrodes are printed on each of a plurality of piezoelectric ceramic green sheets, respectively, then the green sheets are stacked on each other to provide a sheet-stacked piezoelectric body, subsequently two polarizing external electrodes are formed, by, e.g., spattering, on upper and lower surfaces of the stacked piezoelectric body, respectively, and finally a polarizing voltage is applied to the two polarizing external electrodes so as to polarize the stacked piezoelectric body in the direction of stacking of the piezoelectric sheets; and a removing step in which, after the stacked piezoelectric body is polarized in the direction of stacking of the piezoelectric sheets in the polarizing step, the polarizing external electrodes are removed, by, e.g., etching, from the stacked piezoelectric body.
However, in the above-described manufacturing method, the removing step in which the polarizing external electrodes are removed by, e.g., etching from the stacked piezoelectric body, is very cumbersome and time-consuming. This leads to increasing the cost of manufacturing of the stacked piezoelectric body or element. In addition, since the sheet-stacked piezoelectric element is deformed by just producing the electric field in the direction perpendicular to the direction of polarization of the element, the element cannot enjoy a sufficiently high deformation efficiency at an appropriate drive voltage.